1. Field of the Invention
This invention relates generally to devices for interventional therapeutic treatment or vascular surgery for treatment of defects in the vasculature, and more particularly concerns a system and method for delivering intravascular interventional devices, such as for treatment of aneurysms.
2. Description of Related Art
Vascular interventional devices such as vasoocclusive devices are typically placed within the vasculature of the human body by use of a catheter. Vascular interventional devices such as stents can be placed within an occluded vessel to facilitate blood flow through the vessel, and vasoocclusive devices are typically either placed within a blood vessel to block the flow of blood through a vessel making up that portion of the vasculature through the formation of an embolus, or are placed within an aneurysm stemming from the vessel to form such an embolus within the aneurysm. Stents can have a wide variety of configurations, but generally need to be placed and then released at a desired location within a blood vessel. Vasoocclusive devices used for these procedures can also have a wide variety of configurations, and aneurysms have been treated with external surgically placed clips, detachable vasoocclusive balloons and embolus generating vasoocclusive devices such as one or more vasoocclusive coils.
The delivery of such vasoocclusive devices have typically been accomplished by a variety of means, including via a catheter in which the device is pushed through an opening at the distal end of the catheter by a pusher to deploy the device. The vasoocclusive devices can be produced in such a way that they will pass through the lumen of a catheter in a linear shape and take on a complex shape as originally formed after being deployed into the area of interest, such as an aneurysm.
One conventional releasable balloon catheter used to embolize vascular lesions has a tube portion made of a material such as a hydrophilic polymer, located between the catheter and the balloon, that can be melted by heating the tube, or can be dissolved in the blood when heated, and electrodes are provided for heating the tube. Another conventional technique for separating a balloon from a balloon catheter involves the melting and breaking of a connecting member between the balloon and the catheter body, when power is supplied to electrodes provided for heating the connecting member. When the connecting member is heated to temperatures of about 70xc2x0 C. and slight tension is applied, the balloon can be separated from the main catheter body.
An implant delivery assembly is also known that is used for delivery of implants such as embolic coils, utilizing a shape memory decoupling mechanism activated when exposed to body temperature. A cooling solution is flushed through the catheter during introduction and placement of the implant in order to prevent premature release of the implant prior to the time that the implant is to be released. Another implant delivery assembly includes an electrical heating system for heating the coupling mechanism to a temperature at which the shape memory material returns to its original shape, to deploy the implant.
Another device is known in which a device to be implanted is detached by application of a high-frequency current which melts and severs a resin that is used to retain the device to be implanted until the device is to be deployed. In another known device, an electrolytically severable link is dissolved by activation of a power source electrically coupled to the electrolytically severable link to detach the device to be implanted.
In another conventional technique, a conductive guidewire delivers a high frequency current through the guidewire to melt and sever a joint to detach an implanted device from the guidewire. The patient is grounded during the procedure, and current is introduced via the guidewire, rather than with a two way current path.
Such devices that release the interventional device by melting or dissolving the intermediate section between the catheter tip and implanted device may cause thermal damage of surrounding tissues during detachment that can cause embolization in the bloodstream, and may also potentially release undesirable particles of materials into the bloodstream that can also cause embolization in the bloodstream. There is therefore a need for a precise method of deploying therapeutic interventional devices without compromising the position of the implant, without causing thermal damage to surrounding tissues, and without releasing undesirable particles of materials into the bloodstream and risking the, formation of emboli in the bloodstream. The present invention meets these and other needs.
Briefly, and in general terms, the present invention provides for an apparatus for deployment of a therapeutic device such as a micro-coil using a catheter by connecting the therapeutic device to a distal portion of a pusher member. In one presently preferred embodiment, the therapeutic device is detachably mounted to the distal portion of the pusher member by a tubular collar that can be heated by a heater to expand the collar and release and deploy the therapeutic device. In another presently preferred embodiment, the therapeutic device is detachably mounted to the distal portion of the pusher member by a connector thread or fiber passing through a heater provided for heating and breaking the connector fiber to release the therapeutic device. In one presently preferred aspect, the heater is advantageously contained substantially within the distal portion of the pusher member, which provides a sufficient amount of thermal insulation to eliminate the potential for thermal damages of surrounding tissues during detachment, and since the connecting fiber is heated and broken at a location fully contained within the distal portion of the pusher member, the potential for releasing undesirable particles of materials into the bloodstream and consequent embolization in the bloodstream is virtually eliminated.
In one presently preferred embodiment, the invention accordingly provides for an apparatus for release and deployment of a therapeutic device within the vasculature of a patient, comprising an elongated, flexible pusher member having an interior lumen and a distal portion; a tubular collar detachably mounting the therapeutic device to the pusher member for placement of the therapeutic device within the vasculature, the tubular collar being expandable when heated and having a closed configuration engaging a proximal portion of the therapeutic device and an open configuration releasing the therapeutic device; and a heater disposed in the tubular collar of the pusher member for heating the tubular collar to cause the tubular collar to expand and release the therapeutic device for detaching and deploying the therapeutic device from the flexible pusher member when a desired placement of the therapeutic device within the vasculature is achieved. In one presently preferred aspect, the heater comprises an electrical resistance heater coil, and may further comprise a power supply and control unit (which may be combined in a single unit) to supply electrical current to the heater coil. In a first presently preferred implementation of the tubular collar, the tubular collar is formed from a shape memory material, which may for example be a shape memory polymer, or a shape memory alloy. In another presently preferred implementation of the tubular collar, the tubular collar is formed from a thermoplastic material. The therapeutic device may comprise a vasoocclusive device, such as a microcoil.
The present invention also provides for a method for release and deployment of a therapeutic device within the vasculature of a patient, wherein a therapeutic device is provided, to be placed within the vasculature of a patient; an elongated, flexible pusher member is provided, having an interior lumen, and a distal portion; a tubular collar is provided for detachably mounting the therapeutic device to the pusher member for placement of the therapeutic device within the vasculature, the tubular collar being expandable when heated and having a closed configuration engaging a proximal portion of the therapeutic device and an open configuration when heated releasing the therapeutic device; the therapeutic device is positioned at a desired placement within a patient""s vasculature; and said tubular collar is heated to expand said tubular collar for detaching and deploying the therapeutic device from the flexible pusher member when a desired placement of the therapeutic device within a patient""s vasculature is achieved. In a presently preferred aspect of the method, the step of heating the tubular collar comprises passing electrical current through the electrical resistance heater to expand the tubular collar.
In another presently preferred embodiment, the invention provides for an apparatus for release and deployment of a therapeutic device within the vasculature of a patient, which comprises an elongated, flexible pusher member having an interior lumen, and a connector fiber detachably mounting the therapeutic device to the pusher member for placement of the therapeutic device within the vasculature, the connector fiber being capable of being broken by heat. A heater is disposed adjacent to the connector fiber for heating the connector fiber to cause the connector fiber to break and release the therapeutic device for detaching and deploying the therapeutic device from the flexible pusher member when a desired placement of the therapeutic device within the vasculature is achieved. In one currently preferred aspect, the distal portion of the pusher member includes at least one entry port communicating with the interior lumen, with the heater disposed in the interior lumen of the pusher member adjacent to one or more entry ports. In another presently preferred aspect, the connector fiber passes through the heater. In a currently preferred embodiment, the heater comprises an electrical resistance heater coil, and may also comprise a control unit, with the heater connected by electrical connectors to the control unit for supplying electrical current to the heater coil. In presently preferred aspects of the apparatus, the flexible pusher member comprises a heat insulating shaft, and the connector fiber is formed from a thermoplastic material, such as polyethylene.
In one presently preferred embodiment, the therapeutic device to be placed within the vasculature of a patient is connected to an annular connector ring, and the connector fiber mounting the therapeutic device to the pusher member passes through the connector ring to secure the therapeutic device to the pusher member. In a currently preferred aspect, the connector fiber extends from a proximal portion of the pusher member to form a loop through the connector ring, and back through the one or more ports through the pusher member to the proximal portion of the pusher member. In another presently preferred aspect, the therapeutic device comprises a vasoocclusive device, such as a microcoil.
The invention also provides for a method for release and deployment of a therapeutic device within the vasculature of a patient. In the method of the invention, a therapeutic device to be placed within the vasculature of a patient is provided; and an elongated, flexible pusher member. A connector fiber detachably mounts the therapeutic device to the pusher member for placement of the therapeutic device within the vasculature, with the connector fiber being capable of being broken by heating, and the therapeutic device is positioned at a desired placement within a patient""s vasculature. Thereafter, a portion of the connector fiber is heated to break the portion of the connector fiber for detaching and deploying the therapeutic device from the flexible pusher member when a desired placement of the therapeutic device within a patient""s vasculature is achieved. In a presently preferred aspect of the method, the portion of the connector fiber to be broken is passed through an electrical resistance heater disposed within the lumen of the flexible pusher member, and the step of heating the portion of the connector fiber comprises passing electrical current through the electrical resistance heater to break the portion of the connector fiber.